Normally, online safety and stability defense systems of Chinese grids (state grid and province grids) feature online preventive control assistant decision making functions for safety and stability of power grids. These functions automatically search preventive control measures that restore system safe status at minimum cost from specified set of candidate preventive control measures (control equipment, control range, and control cost) according to grid real-time operating conditions and results of safety and stability assessment of the grid, so as to allow preventive control assistant decision making by dispatchers.
In present online defense systems, basically fixed set of candidate control measures specified in advance is used. In the environment of external calamity, control capability and control cost of candidate control measures may vary. If existing set of candidate measures is still used, result of preventive control decision may not be economic and even feasible, so that effective preventive control assistant decision making is not available to dispatchers.
At present, some research organizations have studied effect of natural calamities (e.g. typhoon, lighting, and ice covering) on power equipment, particularly fault probability of power transmission lines, and developed related probability assessment technique. This has laid a good foundation for assessment of effect of calamities on equipment inside stations (units and buses etc.) and dynamic adjustment of the set of candidate control measures.